I am using iAS. What is the efficiency of the iAS Connection Pool? Is it necessary to create my own list of connections that I can use to get connections from pool that iAS provides?

Let me explain:
I want to create a list of Connection objects in my servlet, which will hold a bunch of open connections to the pool that iAS provides. Any of my servlets that want a DB connection will grab a connection from this servlet. Will this kind of a setup add to the speed of database access? Or will it add an extra overhead and slow down my application in any way? I have a friend who says he did this with Java Web Server and found that his DB access speed increased.